Speedy they're not, but the Kilobots – a group of 1,024 low-cost, inch-wide robots that can self-organize into complex shapes – together comprise the largest, most technically impressive robotic swarm ever created.

In current robotics research there is a vast body of work on algorithms and control methods for groups of decentralized cooperating robots, called a swarm or collective. These algorithms are generally meant to control collectives of hundreds or even thousands of robots; however, for reasons of cost, time, or complexity, they are generally validated in simulation only, or on a group of a few 10s of robots. To address this issue, we designed the Kilobot, a low-cost robot designed to make testing collective algorithms on hundreds or thousands ("kilos") of robots accessible to robotics researchers. Each robot has the basic capabilities required for a swarm robot, but is made with low-cost parts, and is mostly assembled by an automated process.

In the latest issue of Science, Rubenstein and his colleagues report the most impressive demonstration of robotic swarm activity to date: A group of 1,024 Kilobots twitching, scuttling, and jostling their way into a variety of two-dimensional shapes — two-dimensional in the sense that the shapes are never more than one-Kilobot tall. That's still several orders of magnitude shy of the swarms we see in nature (the number of ants in a supercolony, for example, can easily exceed 100-million), but it's a significant step for the field of swarm robotics. As Rubenstein and his colleagues note, their work advances the ambitious goal "of creating artificial swarms with the capabilities of natural ones."

Unsurprisingly, designing massively scalable, self-assembling robots on the cheap has not been easy. Challenges range from practical in nature (e.g., what is the most time-effective way to power-on more than a thousand robots – you can't exactly give each one a power switch, can you?) to choreographic. It is more cost effective for a Kilobot to get its bearings by communicating with other Kilobots, for example, than to know its own position in space. By following a set of simple rules, recounted in detail here by NatGeo's Ed Yong, the Kilobots can cooperate to form a designated shape, be it a star, a letter, or, someday, perhaps something more functional.

"Increasingly, we're going to see large numbers of robots working together, whether it's hundreds of robots cooperating to achieve environmental clean-up or a quick disaster response, or millions of self-driving cars on our highways," said Nagpal, in a statement. "Understanding how to design 'good' systems at that scale will be critical," she said.